This application relates to wastewater treatment, and more particularly to elimination of fibers on a mixer impeller in wastewater treatment. Sewage treatment involves the removal of contaminants from waste water and household sewage to produce solid or semisolid waste and an effluent suitable for discharge back into the environment. Sewage is created by residential, institutional, commercial and industrial establishments and includes household waste, liquid from toilets, baths, showers, kitchens, sinks, etc.
Conventional sewage treatment may involve primary, secondary and tertiary treatment steps. During primary treatment, sewage is held in a basin where heavy solids generally settle and light contaminants float to the surface. The sediment and floating materials are removed and the remaining liquid may be discharged or subject to secondary treatment. Secondary treatment generally removes dissolved and suspended biological matter and is performed by introducing micro organisms in a managed habitat. Secondary treatment may require a separation process to remove the micro organisms from the water prior to discharge or to tertiary treatment. In tertiary treatment treated water is sometimes disinfected chemically or physically prior to discharge to the environment.
Many municipal plants churn the sewage constantly during treatment steps to encourage separation and to introduce oxygen to allow the micro organisms to consume the biodegradable soluble organic contaminants like sugars, fats, etc. Some systems use aerated lagoons in which an electric motor driven impeller draws air into the water to allow the micro organisms to function efficiently.